Gambling is one of the ways.
You could also mention,Gambling is one of the ways to lose his 0.1 btc as fast as possible.Please don't suggest gambling to people who aren't interested in it.Don't lure them to gamble.Could have give some constructive answers like invest/Trade/buy-sell out of 100 other things but gambling.
Yet you chose to promote gambling yourself. Anyhow some gambling sites allow you to play as an investor. That's not 100% safe since site owner can run with the funds. But gambling isn't a ponzi scheme and is profitable in the long run, so why should the owners close their shop. I just invested in BitDice with litecoin and bitcoin. Will see how that goes down the road.